NASA’s Physical Oceanography Distributed Active Archive Center (PO.DAAC) released version 6.0 Soil Moisture Active Passive (SMAP) Sea Surface Salinity (SSS) validated datasets from Remote Sensing Systems (RSS) and sponsored by the NASA Ocean Salinity Science Team. The SMAP satellite was launched on January 31, 2015, with a near-polar orbit at an inclination of 98 degrees and an altitude of 685 km. It has an ascending node time of 6 p.m. and is sun-synchronous. With its 1000 km swath, SMAP achieves global coverage in approximately 3 days, but has an exact orbit repeat cycle of 8 days.
The major changes in Version 6.0 from prior Version 5.0 are: (1) Removal of biases during the first few months (April 2015-August 2015) of the SMAP mission that are related to the operation of the SMAP radar during that time. (2) Mitigation of biases that depend on the SMAP look angle. (3) Mitigation of salty biases at high Northern latitudes. (4) Revised (small change) sun-glint flag.
This release includes level 2C, level 2C near real time (NRT), level 3 mapped monthly, and 8-day running mean datasets. All products are in the netCDF-4 file format and are CF/ACDD metadata conventions compliant. Similar to prior releases, the standard product is the smoothed salinity product with a spatial resolution of approximately 70 km, and the 40-km fields are included for experimental purposes. For most open ocean applications, the standard fields are the best used since they have significantly lower noise than the 40-km data. Please note that no SMAP salinity data are available from 08/09/2022 – 10/06/2022 and 06/19/2019 – 07/23/2019, as SMAP was not in science mode or flying in its nominal orbit during that time. The datasets extend from March 28, 2015, to the present with 4-day latency for L2C, 5-hour latency for L2C NRT, and 7-day latency for both L3 8-day running average and L3 monthly average.
The SMAP RSS datasets and the associated technical documentation are described, discoverable, and accessible via the Earthdata catalog. Users are recommended to download the data using the podaac-data-subscriber. We also encourage users to visit the PO.DAAC Cloud Cookbook for detailed information about how to access the data from NASA Earthdata Cloud.
Reference
Meissner, T., F.J. Wentz, and D.M. Le Vine, 2018, The Salinity Retrieval Algorithms for the NASA Aquarius Version 5 and SMAP Version 3 Releases, Remote Sensing 10, 1121, doi:10.3390/rs10071121.
Citation
T. Meissner, F. J. Wentz, A. Manaster, R. Lindsley, M. Brewer, M. Densberger, 2024: Remote Sensing Systems SMAP Ocean Surface Salinities [Level 2C, Level 2C NRT, Level 3 Running 8-day, Level 3 Monthly], Version 6.0 validated release. Remote Sensing Systems, Santa Rosa, CA, USA. doi: 10.5067/SMP60-2SOCS,10.5067/SMP60-2SNRT,10.5067/SMP60-3SPCS,10.5067/SMP60-3SMCS.
If you have questions, please contact PO.DAAC user services or visit PO.DAAC on Earthdata Forum.